The present invention pertains generally to the field of lighting control. More particularly, the present invention relates to a lighting control system including a wireless, integrated circuit, sensor for detecting light and/or occupancy in an area.
As is well known, fluorescent lamps offer large energy savings as compared to incandescent lamps. Additional energy savings can be obtained through the use of dimmable fluorescent lamp ballasts. These ballasts can be controlled by ballast control circuitry which reduces the level of the light produced by the fluorescent lamp. In this regard, conservation of energy is always an economic and environmental consideration in designing lighting systems.
In addition, as will be appreciated by one skilled in the art, the level and type of background illumination has a profound effect on the optimum artificial light needed for a work area. Besides the ergonomic aspects involved in providing adequate lighting, the light level in an area also affects the human physiology. It is well accepted that lighting can dramatically affect the circadian rhythm of the human physiological system. Accordingly, it is desirable to control the level of the artificial light to provide an optimum amount of light, see, e.g., U.S. Pat. Nos. 5,648,656 and 5,459,376, the contents of which are incorporated herein by reference.
Lighting systems are known that control, i.e., decrease or increase, the level of artificial light in relation to the level of daylight in an area. Generally, these conventional lighting control systems are hampered by the lack of adequate light sensors for flexible daylight harvesting applications. Typically, conventional sensor technology uses a single photodiode that senses the light on a work surface so that the light can be adjusted accordingly to maintain a constant value during the day.
Since such sensors detect light from either one limited position or possibly an averaged value over a predetermined area, it is necessary to carefully position and angle the sensors. This is required to ensure that the sensors detect adequate and accurate illumination data so that a desired light level can be provided throughout the day.
Furthermore, as will be appreciated by one skilled in the art, conventional sensor technology normally requires independent calibration for each application to achieve adequate results. One reason is that typical light sensors, for example, are analog devices that are prone to drift and inaccuracies.
In addition to the light sensors discussed above, separate motion sensors may also be used to detect the movement of an occupant in an area, as described in U.S. Pat. No. 5,489,827, the contents of which are incorporated herein by reference. A light source is turned xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d depending on the presence, or lack thereof, of an occupant in the sensing area. However, determining the state of occupancy within an area can be difficult depending on the positioning of the motion sensor. For example, the motion sensor""s field of view may be limited or obstructed. Moreover, after placement of the motion sensor, subsequent rearrangement of an area""s contents (e.g., furniture) may impair the field of view.
Another shortcoming of such motion sensors is that they are typically battery powered. Eventually, these batteries need to be replaced. This is not only inconvenient from a maintenance perspective, but the need for replacement may not always be readily apparent.
Conventional light and motion sensors also typically have wired connections to the control unit, e.g., ballast. This requirement adds extra cost for installation, as well as the extra cost for the wired interface in the control ballast, which must be isolated for safety reasons. These hard-wired sensors may be in addition to the need for a separate infrared (IR) sensor used by many ballast systems (e.g., Philips ballast systems) to provide a wireless control interface between the ballast and a handheld or wall mounted remote control unit. This IR sensor is usually mounted on the ceiling near the fixture with a wired connection to the ballast, which again adds to the overall system expense and installation time.
Some improvement in lighting control technology has been achieved by using multiple light sensors. In this arrangement, the sensors are tied to a control unit that generates a control signal based on the inputs from the multiple sensors. Illustratively, in the prior art, a ballast dimming signal based on some algorithm of multiple sensor inputs to control a light source is known. This type of arrangement, however, results in complex installation/setup procedures and expensive equipment requirements. Moreover, this arrangement fails to address the shortcomings of conventional sensor technology discussed above.
There thus exists in the art a need for a lighting control system that provides improved performance as well as reducing the cost, complexity and installation/setup time of the system. It is also desirable to provide a sensor that is not encumbered by hard-wired connections and limited-lifetime, power supplies.
It is an object of the present invention to address the limitations of the conventional lighting control systems and sensor technology discussed above.
In one aspect of the present invention, a lighting control system includes a light source having a control unit and a wireless receiver. The system also includes a sensor having a plurality of pixels and a wireless transmitter, which are formed by a single integrated circuit (IC). The sensor transmits data to the light source using the wireless transmitter so that the control unit can control the light source in accordance with the transmitted data.
One advantageous embodiment of the present invention relates to the use of CMOS imaging technology for the sensor. This embodiment enables the integration of multiple functions into one integrated circuit (IC). This results in greatly reduced power requirements as compared to conventional sensors. The IC sensor architecture combines a wireless interface, as well as a pixel array for improved daylight harvesting and occupancy detection. The integration of these multiple functions into a single integrated component results in significant cost savings and reduced (installation/equipment) complexity for the lighting control system and sensor.
These and other embodiments and aspects of the present invention are exemplified in the following detailed disclosure.